Perhaps if the kitchen had just been washed the floor would still be wet. A wet, cold atmosphere was maybe not considered healthy for a person who might have a cold.

Jane might be being genuinely helpful and considerate here, or she might be longing for a respite from Miss Bate's incessant chatter. It might have occurred to Jane that if if Miss Bates went down to the kitchen she would get chatting to Patty, then she would have to relay all the minutiae of the conversation, the salting pan and the wet floor to Jane. In fact she might never leave the house at all and Jane would have no respite!

A few paragraphs later is a real LOL line for me:

"A new neighbour for us all, Miss Woodhouse!" said Miss Bates, joyfully; "my mother is so pleased! she says she cannot bear to have the poor old Vicarage without a mistress. This is great news, indeed. Jane, you have never seen Mr. Elton! no wonder that you have such a curiosity to see him."

Jane's curiosity did not appear of that absorbing nature as wholly to occupy her.